JPWO2019230097A1 - Laminated polypropylene film - Google Patents

Abstract

To provide a laminated polypropylene film having good transferability and adhesion to a printing paint, low charge, and excellent transparency. A laminated polypropylene film having a resin layer on at least one surface of a polypropylene film base material, wherein the resin layer contains at least a polyurethane resin, an ethylene-based copolymer resin, and an antistatic agent, with respect to 100 parts by mass of the polyurethane resin. A laminated polypropylene fill containing 5 parts by mass or more and 50 parts by mass or less of an ethylene-based copolymer resin.

Description

The present invention relates to a laminated polypropylene film having good printability and adhesiveness. More specifically, the present invention relates to a laminated polypropylene film having excellent transferability and adhesion to UV ink in a printing process and also having excellent transparency.

As a packaging material used for foods, pharmaceuticals, industrial products, etc., a film made of plastic such as polyolefin, polyester, or polyamide is often used as a base material. In particular, polypropylene film is widely used in a wide range of applications such as packaging of foods and various products, electrical insulation, and surface protection film due to its excellent mechanical properties, thermal properties, electrical properties, and optical properties.
However, since the polypropylene film does not have a polar group as a functional group due to its molecular structure, the surface wettability is low, and the transferability and adhesion to various printing paints and the like are poor. Further, the polypropylene film has a problem that static electricity is easily generated due to friction in a printing process or the like, and the printed appearance is deteriorated due to adhesion of dust or the like due to the charging.

As a method of imparting adhesion, there is a method of applying a corona discharge treatment, a low temperature plasma treatment, a flame treatment, or the like to the surface of the polypropylene film. By performing these treatments, it is possible to improve the transferability to various printing paints and the adhesion to the printing paint film.
However, these methods have a problem that the print appearance is deteriorated due to charging, and a problem that the transferability and adhesion of the printing paint are changed or deteriorated with time.

As a method for preventing antistatic properties, there is a method of incorporating an antistatic agent in the polypropylene film base material. However, since the antistatic agent in the polypropylene film base material is deposited on the surface with time, the antistatic property of the polypropylene film base material may decrease.

Therefore, a method of laminating a resin layer having transferability and adhesion to a printing paint on a polypropylene film base material has been proposed (see, for example, Patent Document 1).
However, although it is possible to prevent the polypropylene film base material from being charged, the transferability and adhesion to the printing paint are not satisfactory.

Japanese Unexamined Patent Publication No. 2001-107029

An object of the present invention has been made to solve the above problems, that is, to obtain a laminated polypropylene film having good transferability and adhesion to a printing paint, low charge, and excellent transparency. To provide.

As a result of diligent research in order to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is as follows.

The present invention is a laminated polypropylene film having a resin layer on at least one surface of a polypropylene film base material, wherein the resin layer contains at least a polyurethane resin, an ethylene-based copolymer resin, and an antistatic agent, and 100 parts by mass of the polyurethane resin. On the other hand, it is a laminated polypropylene film containing 5 parts by mass or more and 50 parts by mass or less of an ethylene-based copolymer resin.

The glass transition temperature of the polyurethane resin contained in the resin layer is preferably 40 ° C. or lower.

The thickness of the resin layer is preferably 0.03 μm or more and 0.20 μm or less.

The laminated polypropylene film of the present invention has excellent transparency, does not easily deteriorate the printed appearance due to charging, has good transferability and adhesion to the printing paint, and changes little with time. Therefore, various printing paints were used. Since it can be printed and its quality is stable for a long period of time, it can be suitably used as a packaging film for foods and various products. Therefore, it makes a great contribution to the industrial world.

Hereinafter, the present invention will be described in detail.

(Film base material)
In the present invention, the polypropylene film is preferably a biaxially oriented polypropylene film formed by biaxially stretching a polypropylene resin.
The polypropylene-based resin referred to here is selected from the group consisting of an n-heptane-insoluble isotactic propylene homopolymer and a copolymer of propylene containing 70 mol% or more of propylene and another α-olefin. It is preferably made of at least one kind of resin.
Such a polypropylene-based resin preferably contains 80% by weight or more, more preferably 90% by weight or more, based on the resin composition constituting the polypropylene film.
The melting point of the polypropylene-based resin used for the polypropylene film needs to be 156 ° C. or higher. The melting point is measured by the method described in Examples described later. If the melting point is less than 156 ° C., the transfer of the film in the automatic packaging process cannot be made smoother, and the obtained bag-making product is more likely to wrinkle.
The n-heptane insoluble index indicates the crystallinity of polypropylene and at the same time indicates the safety when used for food packaging. In the present invention, n-heptane insoluble according to the February 1982 Ministry of Health and Welfare Notification No. 20. It is a preferable embodiment to use the one having an elution amount of 150 ppm or less when extracted at 25 ° C. for 60 minutes [30 ppm or less when the operating temperature exceeds 100 ° C.]).
By using such a biaxially oriented polypropylene film, it is excellent in mechanical properties, thermal properties, electrical properties, and optical properties, and can be suitably used as a packaging film for foods and various products.

The thickness of the polypropylene film is preferably 10 to 100 μm, preferably 10 to 60 μm, and more preferably about 15 to 50 μm from the viewpoint of film and economy. Further, various additives and stabilizers such as antistatic agent, ultraviolet ray inhibitor, plasticizer, lubricant and the like may be used in the polypropylene film, and corona treatment, low temperature plasma treatment and ion bombard treatment are performed as pretreatment. It may be left as it is, and further subjected to chemical treatment, solvent treatment, or the like.

In the present invention, the haze of the polypropylene film is preferably 3.0% or less. If the haze of the polypropylene film exceeds 3.0%, the transparency of the laminated polypropylene film is inferior and the visibility of printing is lowered.

(Resin layer)
The resin layer used in the present invention is provided on at least one surface of the polypropylene film substrate. The resin layer contains at least a polyurethane resin, an ethylene-based copolymer resin, and an antistatic agent.

(Polyurethane resin)
The above-mentioned polyurethane resin contains at least a polyol-derived component and a polyisocyanate-derived component as constituent components, and further contains a chain extender, if necessary. The polyurethane resin of the present invention is a polymer compound in which these constituent components are copolymerized mainly by urethane bonds.

Examples of the polyol include polyester polyol, polyether polyol, polycarbonate polyol, polyolefin polyol, acrylic polyol and the like.

The polyester polyol includes, for example, polyvalent carboxylic acids such as malonic acid, succinic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, and isophthalic acid, or acid anhydrides thereof, and, for example, ethylene glycol and diethylene glycol. , Triethylene glycol, propylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, neopentyl glycol, 1,6-hexanediol and other polyhydric alcohols can get.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

Among these polyols, polyester polyols are preferable in terms of water resistance, and polyols obtained from adipic acid, sebacic acid, terephthalic acid, and isophthalic acid are particularly preferable.

Examples of the polyisocyanate include aromatic diisocyanates, aromatic aliphatic diisocyanates, alicyclic diisocyanates, aliphatic diisocyanates, and polyisocyanates in which a single compound or a plurality of these compounds are added in advance with trimethylolpropane or the like.

Examples of the aromatic diisocyanate include tolylene diisocyanate and diphenylmethane-4,4-diisocyanate.
Examples of the aromatic aliphatic diisocyanate include xylylene diisocyanate.
Examples of the alicyclic diisocyanate include isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis (isocyanatemethyl) cyclohexane.
Examples of the aliphatic diisocyanate include hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate.

Among these, aromatic diisocyanates are preferable, and tolylene diisocyanates are particularly preferable.

Examples of the chain extender include short chain diols and short chain diamines. Examples of the short chain diol include ethylene glycol and tetramethylene glycol. Examples of the short chain diamine include ethylenediamine and tetramethylenediamine.

The polyurethane resin used in the present invention preferably has a glass transition temperature of 40 ° C. or lower. If the temperature exceeds 40 ° C., the adhesion of UV ink or the like may decrease, and the compatibility with the antistatic agent decreases in the process of applying and drying the resin layer, so that the wettability and antistatic properties suitable for printing suitability are reduced. It is not possible to achieve both sex.

The polyurethane resin used in the present invention is said to use a coating liquid containing the same to reduce the burden on the environment when forming the resin layer and to suppress the residual organic solvent in the formed resin layer. From the viewpoint, it is preferably dissolved in an aqueous solvent. The water-based solvent referred to here means water or a mixed solvent of water and an alcohol solvent. The mixing ratio of water and the alcohol solvent is preferably 100/0 to 50/50 (% by weight).

In order for the polyurethane resin to dissolve in an aqueous solvent, a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. Since the sulfonic acid (salt) group is strongly acidic and it may be difficult to maintain moisture resistance due to its moisture absorption performance, it is preferable to introduce a weakly acidic carboxylic acid (salt) group. It is also possible to introduce a nonionic group such as a polyoxyalkylene group.

In order to introduce a carboxylic acid (salt) group into a polyurethane resin, for example, as a polyol component, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid is introduced as a copolymerization component to form a salt. Neutralize with agent. Specific examples of the salt forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and tri-n-butylamine, and N such as N-methylmorpholin and N-ethylmorpholin. Examples thereof include N-dialkylalkanolamines such as −alkylmorpholins, N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

When a polyol having a carboxylic acid (salt) group is used as a copolymerization component, the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the polyurethane resin is 100 mol% of the total polyisocyanate component of the polyurethane resin. When it is used, it is preferably 3 to 60 mol%, preferably 5 to 40 mol%. If the composition molar ratio is less than 3 mol%, water dispersibility may become difficult. Further, when the composition molar ratio exceeds 60 mol%, the water resistance may decrease.

(Ethylene copolymer)
The ethylene-based copolymer used in the resin layer of the present invention means a copolymer of ethylene and an α-olefin other than ethylene. It is preferable that the α-olefin contains an alkene having 3 or more carbon atoms.

The ethylene-based copolymer and polyurethane resin used in the present invention use a coating liquid containing the same to reduce the burden on the environment when forming the resin layer, and the organic solvent in the formed resin layer. From the viewpoint of suppressing residue, it is preferably dissolved in an aqueous solvent. The water-based solvent referred to here means water or a mixed solvent of water and an alcohol solvent. The mixing ratio of water and the alcohol solvent is preferably 100/0 to 50/50 (% by weight). In order for the ethylene-based copolymer to dissolve in an aqueous solvent, it is preferable that the α-olefin contains acrylic acid, methacrylic acid, or a salt thereof.

Such as, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylate copolymer, ethylene- (meth) acrylic acid ester- (meth) acrylic acid copolymer, ethylene-( Meta) Acrylic acid ester- (meth) acrylate copolymer, ethylene- (meth) acrylic acid-maleic anhydride copolymer, ethylene-acrylic acid-maleic anhydride copolymer, and ethylene-glycidyl (meth) ) Acrylic acid ester copolymer, and further, a copolymer with 1-alkene can be mentioned.
Among these, ethylene- (meth) acrylate-1-alkene copolymer is preferable, and ethylene-acrylate-1-alkene copolymer is particularly preferable in terms of adhesion to UV ink.

The content of the ethylene-derived component in the ethylene-based copolymer is preferably 50% by weight or more from the viewpoint of adhesiveness to the base film.

It is important that the ethylene-based copolymer used in the resin layer of the present invention contains 5 parts by mass or more and 50 parts by mass or less of the ethylene-based copolymer resin with respect to 100 parts by mass of the polyurethane resin. If the amount of the ethylene-based copolymer is less than 5 parts by mass, the adhesiveness to the base film is lowered, and the antistatic agent cannot move to the surface in the process of applying and drying the resin layer, so that the antistatic property is provided. Not satisfied. Further, if the ethylene-based copolymer exceeds 50 parts by mass, the adhesion to the UV ink is lowered, and the antistatic property is excessively present on the surface, so that the transferability is lowered and it is not suitable for printing. ..

(Antistatic agent)
The antistatic agent used in the resin layer of the present invention consists of a group selected from alkylamine derivatives, fatty acid amide derivatives, polyhydric alcohol esters, alkylsulfonates, alkylbenzenessulfonates, alkylsulfates, alkylphosphates, and quaternary ammonium salts. At least one compound is mentioned.

Examples of the alkylamine derivative include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl amine.
Examples of the fatty acid amide derivative include an alkylamine derivative and hydroxystearic acid mide.
Examples of the polyhydric alcohol ester include a glycerin fatty acid ester.
Examples of the quaternary ammonium salt include quaternary ammonium chloride, quaternary ammonium sulfate, and quaternary ammonium nitrate.
Among these, quaternary ammonium chloride is preferable in terms of antistatic property.

It is important that the antistatic agent used for the resin layer of the present invention contains 20 parts by mass or more and 70 parts by mass or less of the antistatic agent with respect to 100 parts by mass of the polyurethane resin. If the amount of antistatic agent is less than 20 parts by mass, the antistatic property is lowered. On the other hand, if the amount of the antistatic agent exceeds 70 parts by mass, the adhesion to the UV ink is lowered, and the antistatic property is excessively present on the surface, so that the transferability is lowered, which is not suitable for printing.

(Additive)
In order to impart other functionality to the resin layer, various additives may be contained as long as the object of the present invention is not impaired. Examples of the additive include surfactants, fluorescent dyes, fluorescent whitening agents, plasticizers, ultraviolet absorbers, pigment dispersants, defoaming agents, defoaming agents, preservatives, lubricants and the like.

(Other layers)
In the present invention, another antistatic layer, another resin layer, an adhesive layer, an easy-to-slip layer, a dye, a pigment, or the like is provided on the surface of the film substrate on which the resin layer is not provided, as long as the effect of the present invention is not impaired. Other functions such as a resin layer containing the dye of the above may be imparted.

(Production method)
In the present invention, as a method of laminating resin layers, a coating liquid containing a polyurethane resin, an ethylene-based copolymer resin, and an antistatic agent is dissolved or dispersed, and then dried. The method of causing is preferable. Known coating methods such as gravure coating method, kiss coating method, dip method, spray coating method, curtain coating method, air knife coating method, blade coating method, reverse roll coating method, bar coating method, and lip coating method are available. Can be mentioned.

The thickness of the resin layer after coating and drying depends on the required degree of resin layer property and antistatic property, but is preferably 0.03 μm or more and 0.20 μm or less, and the lower limit is 0.05 μm. As mentioned above, the upper limit is preferably 0.15 μm or less. If the thickness of the resin layer is thinner than 0.03 μm, it is difficult to obtain the transferability, adhesion, and antistatic property of the printing paint. On the other hand, if it exceeds 0.20 μm, there is no significant improvement in performance, and coating / coating This is not preferable because it leads to an increase in the load during drying and an increase in manufacturing cost.

Examples of the method of applying the coating liquid on the film substrate and then drying it include known hot air drying and infrared heaters, but hot air drying having a high drying speed is preferable.

The drying temperature after coating is preferably 40 ° C. or higher and 150 ° C. or lower, and particularly preferably the lower limit is 45 ° C. or higher and the upper limit is 120 ° C. or lower. If the temperature is lower than 40 ° C., the solvent contained in the coating liquid cannot be sufficiently removed, and problems such as brushing may occur. On the contrary, when the temperature exceeds 150 ° C., minute defects of the coating film such as fine coating missing, fine repellent, and cracks derived from bubbles are likely to occur, and the appearance may be deteriorated. Further, the film base material is strongly shrunk by heat, and the flatness of the film base material is deteriorated due to heat wrinkles, and the mechanical properties of the base film are deteriorated.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is naturally not limited to the following Examples. The film properties obtained in each example were measured and evaluated by the following methods.

(Evaluation method)
(1) Thickness of resin layer A sample was prepared by the following method and observed using a transmission electron microscope. First, the obtained resin layered polypropylene film was cut out perpendicular to the flow direction of the film and embedded in an epoxy resin. As the epoxy resin, a well-mixed epoxy resin of Luabeck 812, Luabeck NMA (manufactured by Nacalai Tesque), and DMP30 (manufactured by TAAB) at a weight ratio of 100: 89: 3 was used. After embedding the sample film in the epoxy resin, the sample film was left in an oven adjusted to a temperature of 60 ° C. for 16 hours to cure the epoxy resin to obtain an embedding block.
The obtained embedding block was attached to Ultracut N manufactured by Nissei Sangyo Co., Ltd. to prepare an ultrathin section. First, trimming was performed using a glass knife until the cross section of the portion to be used for observing the film appeared on the resin surface. Next, an ultrathin section was cut out using a diamond knife (Sumitomo Electric Industries, Ltd., Sumiknife SK2045). The cut out ultrathin sections were collected on a mesh and then thinly vapor-deposited with carbon.
The electron microscope observation was carried out using JEM-2010 manufactured by JEOL Ltd. under the condition of an acceleration voltage of 200 kV. The thickness of the resin layer was measured from the image obtained by electron microscopy of the cross section of the film.

(2) Glass transition temperature In accordance with JIS K7121, using a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments), 10 mg of urethane resin sample is heated at 20 ° C./min over a temperature range of 25 to 300 ° C. The external glass transition start temperature obtained from the DSC curve was defined as the glass transition temperature.

(3) Surface free energy After leaving the sample of the resin layered polypropylene film in an atmosphere of 50% relative humidity for 24 hours, the resin layer was used using a FACE contact angle meter (manufactured by Kyowa Surface Chemical Co., Ltd., CA-X type). The contact angle between distilled water and diiodomethane 1 minute after dropping on the layer side was measured. The measurement was performed 5 times for each sample, and the average value of the three measured values excluding the maximum value and the minimum value of the measured values was taken as the contact angle. Here, the surface free energy γs was calculated from the contact angle between distilled water and diiodomethane, and those having a surface free energy γs of 45 to 60 mN / m were judged to have wettability.

(4) The measurement was performed using a turbidity meter (Nippon Denshoku Co., Ltd., NDH2000) in accordance with Haze JIS K7136.

(5) Surface resistance The surface resistance of the resin layer layer surface of the resin layer polypropylene film is measured under the conditions of an applied voltage of 500 V, 20 ° C., and 55% RH using a surface resistance meter (Mitsubishi Chemical Corporation, Lorester UP MCP-HT450). Measured in. When the value of the surface resistance is 14.0 log (Ω / □) or less, it is judged to have antistatic property, and especially when the value of the surface resistance is 13.0 log (Ω / □) or less, it is judged to be good.

(6) Transferability A UV ink (T & K TOKA Co., Ltd., Best Cure UV161 Indigo S) is printed on the resin layer surface side of the transferable resin layered polypropylene film using a RI tester (Ming Seisakusho Co., Ltd., model number RI-3). A print sample was obtained by passing the film at a speed of 10 m / min at a position 20 cm under a high-pressure mercury lamp having an output of 120 W / cm (integrated light amount 100 mJ / cm ^2). Visually observe the degree of print appearance of the print sample, rank A for those with good transferability without ink fading or printing unevenness, and observe ink fading or printing unevenness in an area less than 10% of the printing area. The one to be printed was judged to be rank B, and the one in which faint ink or uneven printing was observed in an area of 10% or more of the printing area was judged to be rank C. Those having a printability rank of A or B were considered to have printability, and those having a rank of A were particularly judged to be good.

(7) Adhesion The print sample obtained above is cut into 100 grid-like cuts that penetrate the ink layer and reach the resin layer polypropylene film using a cutter guide with a gap spacing of 2 mm. Next, a cellophane adhesive tape (manufactured by Nichiban Co., Ltd., No. 405; 24 mm width) was attached to the cut surface in the shape of a grid and rubbed with an eraser to completely adhere to the cut surface. After that, the cellophane adhesive tape is vertically peeled off from the ink layer surface once, and then the number of squares peeled off from the ink layer surface of the print sample is visually counted, and the ink layer and the resin layer polypropylene film are calculated from the following formula. Adhesion with was sought. In addition, those that were partially peeled out of the squares were also counted as peeled squares and ranked according to the following criteria.
Adhesion (%) = (1-Number of peeled squares / 100) x 100
A: 100% or ink layer material breakage B: 99-70%
C: 69-0%
Those having a printability rank of A or B were judged to have adhesiveness, and those having a rank of A were particularly judged to be good.

The resins, compounds, and solvents used for the resin layer are as follows.
(A-1: Water-dispersible polyurethane resin)
Hydran AP-201 (manufactured by DIC, glass transition temperature: 10 ° C., polyester urethane obtained from polyol consisting of terephthalic acid, isophthalic acid, sebacic acid, adipic acid and tolylene diisocyanate)
Hydran AP-40N (manufactured by DIC, glass transition temperature: 40 ° C., polyester urethane obtained from polyol consisting of terephthalic acid, isophthalic acid, sebacic acid, adipic acid and tolylene diisocyanate)
Hydran AP-30F (manufactured by DIC, glass transition temperature: 60 ° C., polyester urethane obtained from polyol consisting of terephthalic acid, isophthalic acid, sebacic acid, adipic acid and tolylene diisocyanate)

(A-2: Acrylic resin)
John Krill PDX-6102B (manufactured by BASF, glass transition temperature: 25 ° C, styrene-acrylic acid copolymer)

(B: Ethylene copolymer resin)
Hi-Tech S-9201 (manufactured by Toho Chemical Industry Co., Ltd., ethylene-methacrylic acid-1-alkene copolymer)

(C: Antistatic agent)
Elecut C-048 (manufactured by Takemoto Oil & Fat Co., Ltd., quaternary ammonium chloride)

(2: Solvent)
Water / isopropanol = 70/30 solution

(Examples 1 to 6, Comparative Examples 1 to 5)
A coating liquid used for forming a resin layer is applied by a gravure coat on a corona-treated surface of a biaxially oriented polypropylene film (P2108 manufactured by Toyobo Co., Ltd., thickness 40 μm), dried at a temperature of 100 ° C. for 30 seconds, and subjected to Examples 1 to 1. 6 and the resin layered polypropylene films of Comparative Examples 1 to 5 were obtained.
The composition of the coating liquid used for forming the resin layer and the thickness of the resin layer after coating and drying are as shown in Table 1.
The characteristics of the obtained laminated polypropylene film are as shown in Table 1.

The laminated polypropylene films of Examples 1 to 6 satisfied the transferability and adhesion to UV ink while having antistatic properties.

On the other hand, in Comparative Example 1 and Comparative Example 4, the transferability to the UV ink could not be satisfied because there was no urethane resin.
In Comparative Example 2, since the ratio of the ethylene resin to the urethane resin was large, the transferability to the UV ink could not be satisfied.
In Comparative Example 3, since there was no ethylene resin, the adhesion to the UV ink could not be satisfied.
Comparative Example 5 had no antistatic property because it had no antistatic property.

The laminated polypropylene film of the present invention has good transferability and adhesion to printing paints, and can impart antistatic properties without deteriorating the former function, and is easy to handle during printing. However, since it is excellent in transparency and design as a packaging material, it can be widely used in the packaging field.

Claims (3)

A laminated polypropylene film having a resin layer on at least one surface of a polypropylene film base material, wherein the resin layer contains at least a polyurethane resin, an ethylene-based copolymer resin, and an antistatic agent, with respect to 100 parts by mass of the polyurethane resin. A laminated polypropylene film containing 5 parts by mass or more and 50 parts by mass or less of an ethylene-based copolymer resin. The laminated polypropylene film according to claim 1, wherein the glass transition temperature of the polyurethane resin contained in the resin layer is 40 ° C. or lower. The laminated polypropylene film according to claim 1 or 2, wherein the thickness of the resin layer is 0.03 μm or more and 0.20 μm or less.